Hermetically sealed electromagnetic relays are used for switching of high electrical currents and/or high voltages, and typically have fixed and movable contacts, and an actuating mechanism supported within a hermetically sealed chamber. To suppress arc formation, and to provide long operating life, air is removed from the sealed chamber by conventional high-vacuum equipment and techniques. In one style of relay, the chamber is then sealed so the fixed and movable contacts contact in a high-vacuum environment. In another common style, the evacuated chamber is backfilled (and sometimes pressurized) with an insulating gas (e.g., sulphur hexafluoride) with good arc-suppressing properties.
For purposes of this disclosure, a hermetic seal means a seal which is sufficiently strong and impermeable to maintain for a long term a high vacuum of 10−5 Torr (760 Torr=one atmosphere) or less, and a pressure of at least 1.5 atmospheres.
In one embodiment described below, a sealed electromagnetic relay assembly is provided comprising a first relay having a plurality of leads for connection to external circuitry; a plurality of permanent magnets coupled to the first relay proximate to first and second contacts; and a hermetically sealed housing assembly enclosing the first relay. The housing assembly comprises: an upper closure including an evacuation tube in fluid communication with an interior chamber of the housing assembly, wherein ambient air may be evacuated from the housing assembly to a vacuum and wherein the housing assembly, after evacuation, is backfilled with an insulative gas to a pressure of greater than 1.5 atmospheres; and an impermeable potting cup surrounding the first relay and permanent magnets, the potting cup being adapted to receive the first relay at one end and being open at the other end for the receipt of encapsulating material and engagement with the upper closure, wherein the encapsulating material seals the housing assembly against ambient air intrusion, and the relay leads extend outwardly from the housing assembly.
In another embodiment of the present disclosure, a method of producing a relay assembly is provided including the steps of: providing a first relay having a rating of 30V or less for hotswitching; coupling permanent magnets in proximity to fixed and moveable contacts of the first relay so as to create a magnetic field between the fixed and moveable contacts when the fixed and moveable contacts are spaced apart; sealing the first relay within a vessel; evacuating substantially all ambient air from the vessel; and backfilling the vessel with a desired gas.